Chemical mechanical polishing (CMP) is generally known in the art. For example U.S. Pat. No. 5,177,908 to Tuttle issued in 1993 describes a finishing element for semiconductor wafers, having a face shaped to provide a constant, or nearly constant, surface contact rate to a workpiece such as a semiconductor wafer in order to effect improved planarity of the workpiece. U.S. Pat. No. 5,234,867 to Schultz et. al. issued in 1993 describes an apparatus for planarizing semiconductor wafers which in a preferred form includes a rotatable platen for polishing a surface of the semiconductor wafer and a motor for rotating the platen and a non-circular pad is mounted atop the platen to engage and polish the surface of the semiconductor wafer. Fixed abrasive finishing elements are also known for polishing semiconductor layers. An example is WO 98/18159 PCT application by Minnesota Mining and Manufacturing.
An objective of polishing of semiconductor layers is to make the semiconductor layers as nearly perfect as possible. Finishing pad finishing surfaces can suffer from being overly harsh on a workpiece causing unwanted scratching or other unwanted surface damage thus reducing the perfection of the surface. Further, a pad finishing surface can suffer from having a higher than necessary friction when finishing a workpiece. This higher than necessary friction can lead to unwanted surface damage. During finishing a particle can break away from the workpiece surface forming a workpiece abrasive particle which can scratch or damage the workpiece surface. Current CMP slurries are generally complex chemical slurries and applicant has found the addition of new chemicals, such as finishing aids, can cause instability over time, precipitation of the abrasive particulates and/or agglomeration of the abrasive particulates to form large particles which can cause unwanted scratching to the workpiece surface being finished. Applicant""s findings above have not been disclosed to the public. Further, precipitation and/or agglomeration of the abrasive slurry particulates can have an adverse impact on the economical recycling of slurry for finishing workpiece surfaces by forming the larger particulates which either are not recycled or must be reprocessed at an expensive to decrease their size to be within specification. These unwanted effects are particularly important and deleterious to yield when manufacturing electronic wafers, which require extremely close tolerances in required planarity and feature sizes.
It is an advantage of this invention to reduce the harshness of finishing pads on the workpiece surface being finished. It is an advantage of this invention to reduce unwanted scratching or other unwanted surface damage on the workpiece surface during finishing. It is further an advantage of this invention to reduce the friction during finishing to help reduce unwanted surface damage. It is an advantage of the invention to reduce unwanted damage to the workpiece surface when an abrasive workpiece particle breaks away workpiece surface during finishing. It is an advantage of the current invention to add finishing aids during operative finishing motion to the interface between the workpiece being finished and the finishing element finishing surface which reduces the negative impact on the abrasive slurry stability before finishing and potentially even during finishing. It is further an advantage of the current invention to add finishing aids which can help reduce surface damage due to abrasive particulates to the workpiece surface being finished. It is further an advantage of this invention to help improve yield for workpieces having extremely close tolerances such as semiconductor wafers.
These and other advantages of the invention will become readily apparent to those of ordinary skill in the art after reading the following disclosure of the invention.